Corrugated cardboard is widely used to package goods for transit. Such corrugated cardboard, typically comprises an outer sheet of liner sheet (or “linerboard”) that is glued to a fluted sheet and a second outer sheet of liner is glued to the fluted sheet opposite the first outer sheet to form a composite structure that has a thickness that is greater than a combined thickness of the individual sheets. The increased thickness provides a number of advantages as compared to the properties of a non-corrugated combination of the same sheets would provide. These advantages include at least increased stiffness along an axis along which the flutes extend, greater resistance to incidental damage, and a greater ability to support a load applied along the axis of the flutes.
More recently, a product that is analogous to conventional corrugated cardboard has been introduced that is made by extruding sheets of polystyrene or other materials that are separated by co-extruded but separated joints. Many versions of this type of product are sold by Coroplast, Vanceburg, Ky., USA. This forms essentially a polymeric version of corrugated cardboard having different properties made possible through the use of the polymeric materials so extruded. This form of corrugation is more expensive than conventional corrugation because of the increased use of polymeric materials and further suffers from weaknesses at the joints in that the joints are typically thin polymeric supports which are subject to lateral collapse when subjected to shear forces.
Corrugated cardboard and extruded corrugated, hereinafter collectively referred to as “conventional corrugated materials,” also provide advantages over a solid sheet of cardboard of equivalent thickness in that a solid sheet of cardboard of requires more material than corrugated cardboard and therefore is heaver and more expensive than corrugated material for equivalent thicknesses. For these reasons, corrugated cardboard is popularly applied for use in packaging applications where the weight, cost, resiliency, and an ability to support a stacking load is desirable.
The combination of advantages offered by conventional corrugated materials has also proven value in areas such as signage, light duty structural panels and displays. Accordingly, it is frequently the case that markings are often printed on corrugated cardboard stock. For example, shipping boxes can be printed with decorative colors, trade dress, delivery information, or source indications, as well as information regarding the corrugated material itself, such as edge-crush strength, gross weight, fragile, or this-end-up indicators. Printers typically operate using subtractive color: a substantially reflective receiver (piece of corrugated stock) is overcoated image-wise with cyan (C), magenta (M), yellow (Y), black (K), and other colorants. Markings can include multiple types of content. For example, a box can be printed with text, halftoned photographs, and line-art or other graphics. Additionally, the printed content may vary from one box to another, requiring variable-data printing. However, it is difficult for many high quality printing systems to print on thick stiff corrugated substrates, particularly using high volume presses that are intended for use with thinner more flexible roll fed web media.
For example, U.S. Publication No. 2008/0159786 by Tombs et al., entitled “SELECTIVE PRINTING OF RAISED INFORMATION BY ELECTROGRAPHY,” published Jul. 3, 2008, the disclosure of which is incorporated herein by reference, describes electrophotographic printing using marking particles of a substantially larger size than the standard size marking particles of the desired print image. Tombs et al. also describe using non-pigmented (“clear”) marking particles to overlay raised information on an image. C-shaped toner patterns can be printed on half a sheet, which is then folded over and sealed with the toner to make an envelope. However, these schemes are very limited in the thickness, and therefore in the mechanical strength, they can provide.
Conventional fluted cardboard can be made at low cost through the use of high volume web production processes that can use, for example, an arrangement of patterned rollers, to form a sinusoidal pattern of fluting in the fluted sheets and different types of corrugated cardboard can be made in such a fashion by varying sinusoidal fluting amplitudes and frequencies. However, those properties cannot readily be adjusted depending on the type of product to be packaged. For example, referring to FIG. 3A, a standard cardboard box is generally formed by stamping forming box blank 301 from a rectangular sheet of corrugated board. Box blank 301 is then folded along fold lines 302, and front surface 303 of tab 304 is glued to back surface 305 to form a manufacturer's joint. As a result, the direction F of extension of flutes 306 (FIG. 3B) is set across the entire box. The designer of the box cannot align flutes differently in different portions of the box. This restricts the box designer's freedom to adjust the mechanical characteristics of the box based on its intended use. For example, a box may need to have comparable strengths in the X and Y directions, corresponding to the horizontal portions of the box, but may need enhanced strength along the Z-direction in the vertical portion to permit the stacking of boxes without increasing the weight of the box unnecessarily. This relative strength configuration cannot be provided by conventional corrugated materials.
FIG. 3B also shows first liner sheet 310, second liner sheet 311, and fluted sheet 312 between them. Starch glue is conventionally applied at each area of contact between fluted sheet 312 and liner sheets 310 or 311.
Presently, shipping departments of companies need to stock a wide variety of boxes in order to ship a wide variety of products to customers. The boxes should be close in size, but larger than, the product to ship. Extra space in each box is filled with packing materials that add additional weight and cost. It would be preferable to form a box that accurately fits the specific items to be shipped.
In addition, maintaining an inventory of the packaging materials and boxes cost money and takes up space. To reduce such costs, the boxes themselves are generally acquired in an unprinted form so that they can be used for any of a variety of different products. This requires that any desired product marketing, promotional, or trade dress or authentication indicia be printed on the box during the shipping process when it can be difficult to provide the high quality printing that is required to form a high quality image.
Conventional corrugated materials have structural limitations. For example, the adhesives used in conventional corrugated cardboard are typically starch-based adhesives. Such adhesives are water-soluble rendering these vulnerable to catastrophic failure in the event that such boxes are exposed to water. Other adhesives, such as epoxy, glue and hot-melt glue can be used. However, these adhesives change volume when they cool, producing internal stresses that can weaken the structural integrity of the corrugated cardboard material, make the corrugated material less planar, or create sinusoidal variations in a surface of the corrugated that make the surface less attractive as a surface on which images are to be printed and that make it more difficult to print on such surfaces.
There is, therefore, a need for ways of making corrugated board and packages that permit adjusting the mechanical properties and the directions in which those properties are effective. There is also a need for ways of making board using durable adhesives that do not create internal stresses in the board.
Corrugated structures have mechanical properties superior to the materials they are made from. Composite structures are also used to provide this advantage. A composite structure has a matrix material with one or more reinforcement materials therein. An example of a composite is FR-4 fiberglass, used as a base for printed circuit boards. FR-4 is a weave of glass fibers fixed in place in an epoxy resin. Composite structures are used for a wide range of applications to provide stiffness and other desirable properties. Composite materials can be formed in curved shapes and other shapes difficult to make with other similarly-strong materials.
However, the manufacturing of composite materials, especially in curved shapes, is generally energy intensive, time consuming, and expensive. For example, to produce a composite panel can require individual steps of selecting the materials, applying adhesive in a desired pattern on a first surface of a first sheet, contacting a first surface of a second sheet against the first surface of the first sheet and pressing them together, often using a mold and while subjecting the combination of the first and second sheet to heat to set or cure the adhesive. These steps can be repeated to build a composite with more than two sheets. After fabrication, the composite structure is trimmed to the proper size. Each composite shape to be produced requires separate molds, increasing the cost of production tooling.
Despite these limitations, composite structures are commonly used, for example, as curved panels on the interior of aircraft and partitions used to separate office spaces. There is a continuing need, therefore, for producing composite structures more quickly and inexpensively. Moreover, as product cycle times become shorter, there is an increasing need for ways of producing composite structures without first building expensive tooling.